Orthodontics

Question 1

what are the elements of a removal appliance ?

Answer 1

active components, retentive components, baseplate, anchorage

Question 2

which elements of a removal appliance should be designed first ?

Answer 2

active components

Question 3

what should an ideal spring be like ?

Answer 3

apply the correct force over a good range of movement, 
move tooth in the right direction,
be difficult to position incorrectly,
be resistant to accidental damage, 
be atraumatic,
be hygienic

Question 4

what are the 3 parts of the palatal retractor ?

Answer 4

arm, coil, tag

Question 5

what is the unction of the tag?

Answer 5

mechanical retention

Question 6

what factors determine the force applied by palatal springs ?

Answer 6

length of the spring,
thickness of the wire,
elastic modulus of the wire,
degree of activation

Question 7

how does length affect the stiffness of a wire ?

Answer 7

double the length of wire will reduce stiffness by a factor of 8

Question 8

how does thickness affect the stiffness of wire ?

Answer 8

double the radius of a wire will increase the stiffness by a factor of 16

Question 9

how does modulus affect the stiffness of a wire ?

Answer 9

lower modulus means lower stiffness

Question 10

how does degree of activation affect the force applied by a spring ?

Answer 10

double the activation doubles the force

Question 11

how much force should a palatal retractor apply ?

Answer 11

20-40gm (cN) with a 3mm activation

Question 12

what thickness of wore is used to make a palatal retractor ?

Answer 12

0.5mm

Question 13

what can happen if a spring is activated >3mm ?

Answer 13

self insert on the wrong side of the tooth,

apply too much force

Question 14

what is the function of a palatal spring ?

Answer 14

mesio-distal movement of canines, premolars and molars

Question 15

what other orthodontic springs can be used in removable appliances ?

Answer 15

buccal canine retractor, 
Z springs, 
T springs, 
auxiliary springs, 
screws

Question 16

what diameter wire is the self supporting buccal retractor made of ?

Answer 16

0.7mm ss wire

Question 17

what are the advantages of the self supporting buccal retractor ?

Answer 17

stiff so good control of spring position

Question 18

what are the disadvantages of the self supporting buccal retractor ?

Answer 18

activation of stiff wire provides high force levels,

high in sulcus and can traumatise mucosa

Question 19

by how much should a self supporting buccal retractor be activated ?

Answer 19

1mm

Question 20

what diameter wire is the sleeved buccal retractor made from ?

Answer 20

0.5mm ss wire in tubing

Question 21

what are the advantages of the self sleeved buccal retractor ?

Answer 21

flexible,

good control

Question 22

what are the disadvantages of the self sleeved buccal retractor ?

Answer 22

high in sulcus and can traumatise mucosa

Question 23

by how much should a sleeved buccal retractor be activated by ?

Answer 23

2mm

Question 24

what diameter wire is the reverse loop buccal retractor made of ?

Answer 24

0.7mm ss wire

Question 25

how is the reverse loop retractor activated ?

Answer 25

curl and cut

Question 26

what are the advantages of the revere loop buccal retractor ?

Answer 26

short vertically so less traumatic, | good lateral control of spring position

Question 27

what are the disadvantages of the reverse loop buccal retractor ?

Answer 27

stiff so short range

Question 28

by how much should the reverse loop retractor be activated ?

Answer 28

1mm

Question 29

what is the function of Z springs ?

Answer 29

push teeth labially

Question 30

what are the advantages of Z springs ?

Answer 30

flexible with 1-2 mm activation on a single tooth spring and 3-4 mm on a double tooth spring, easily adjustable

Question 31

what are the disadvantages of Z springs ?

Answer 31

displaces the appliance so requires very good retention

Question 32

what is the function of T springs ?

Answer 32

push teeth buccally

Question 33

how are T springs activated ?

Answer 33

pull away from acrylic

Question 34

what are the advantages of T springs ?

Answer 34

easily adjustable, | good for buccal segment teeth

Question 35

what are the disadvantages of T springs ?

Answer 35

displace the appliance and and need good retention, | limited range of action

Question 36

what is the function of screws ?

Answer 36

mesio-distal movement, | expansion

Question 37

What are the elements of a removable appliance ?

Answer 37

Active components, Retentive components, Anchorage, Baseplate

Question 38

What provides retention of a removable appliance on posterior teeth ?

Answer 38

Adam's clasp

Question 39

What provides retention for a removable appliance on anterior teeth ?

Answer 39

Southend clasp, | Labial bow

Question 40

What is an Adams clasp made from ?

Answer 40

0.7mm wire, may be made from 0.6 mm ss wire for premolars

Question 41

What is a Southend clasp made from ?

Answer 41

0.7 mm ss wire

Question 42

What is a labial bow made from?

Answer 42

0.8 mm ss wire

Question 43

what are the functions of the labial bow ?

Answer 43

retention in the mouth, guidance of canines during retraction, actively retract the incisors, retain teeth in corrected position

Question 44

what are the 2 types of labial bow ?

Answer 44

high labial bow - only suited as active component, | reverse looped bow

Question 45

where should the labial bow be positioned in order to be retentive ?

Answer 45

placed at bottom 1/3 of incisors in line with the baseplate

Question 46

how can the labial bow control tooth movement ?

Answer 46

teeth move at right angles to point of contact of the spring, where the line of force does not pass through the centre of resistance, the tooth will rotate retract upper canines and reduce overbite, retract proclined incisors

Question 47

what type of wire is needed for retention in the mouth, canine guidance and retaining tooth positions ?

Answer 47

stiff, thick wire

Question 48

what type of wire is needed to retract incisors ?

Answer 48

flexible wire

Question 49

how does splitting a labial bow aid incisor retraction ?

Answer 49

makes it more flexible

Question 50

what does a removable appliance do ?

Answer 50

tips teeth, does not move roots

Question 51

what are the potential problems from just tipping teeth ?

Answer 51

aesthetic, dental health, occlusion

Question 52

what limitations arise from tipping action ?

Answer 52

mesio-distal in buccal segments, labio-lingual in class II, labio-lingual in class III, mesio-distal in labial segments

Question 53

what are the limitations of removable appliances ?

Answer 53

``` tipping, inappropriate for lower arch, vertical movements, inter arch elastics, precision, rotations, multiple tooth movements ```

Question 54

what are the current uses of removable appliances ?

Answer 54

``` space maintenance, retainers, tooth over the bite, bite opening, expansion, other simple tooth movements ```

Question 55

what are the advantages of removable retainers ?

Answer 55

``` all teeth can be retained, partial withdrawal possible, less dental health hazard, oral hygiene, missing teeth can be replaced, responsibility of the patient ```

Question 56

what are the disadvantages of removable retainers ?

Answer 56

rotations, anterior diastemas, vertical tooth position, need to be worn

Question 57

what are the advantages of the acrylic baseplate ?

Answer 57

can provide anterior and posterior bite planes, can accommodate a screw, give some anchorage from the plate

Question 58

what are the functions of screws ?

Answer 58

unilateral or bilateral distal movement, arch expansion, anterior cross bite correction

Question 59

how can you tell if a patient is wearing their removable appliance ?

Answer 59

``` good speech, palatal gingivitis, wear facets on acrylic, passive springs, confident removal and insertion ```